Control of admission to a communication network makes it possible to decide to accept or to deny a request to use resources of the network, as a function of certain criteria. It may in particular allow effective use of the resources of the network, in particular by denying a request to use resources which would be liable to bring about congestion of the network.
It is beneficial to put such admission control in place in communication networks of IP (for ‘Internet Protocol’) type. Networks of this type make it possible to offer various services such as telephonic services (VoIP for ‘Voice over IP’), video telephony (V2oIP for ‘Voice and Video Internet Protocol’) or else video broadcasting (IPTV for ‘Internet Protocol TeleVision’).
In such IP networks, it is possible to perform transmissions of packets according to a point-to-point link, termed a unicast IP link, or else according to a point-to-multipoint link, termed a multicast IP link or multibroadcast link. According to the latter type of link, the multicast IP packets are conveyed over the IP network and are replicated from a location relatively close to the recipient multicast terminals. This mode of transport makes it possible to establish unidirectional point-to-multipoint connectivity between an arbitrary unicast IP source address and a plurality of IP terminals, and thus to broadcast packets to these terminals in particular within the framework of a multibroadcast service for digital contents such as video contents for example.
In order to receive a content which is broadcast in the network according to a multicast transmission, a terminal subscribes to a corresponding multicast IP address. Next, subsequent to this subscription, it receives the content through multi-broadcasting.
In certain cases, the interface for access of a terminal thus subscribed to one or more multibroadcast services may be congested. Such congestion may degrade the quality of the multibroadcast service at the level of this terminal.
In order to avoid this type of congestion, document US2008112324 proposes the putting in place of an admission control which decides to accept or to deny a new subscription of a terminal to a multibroadcast service by taking into account the number of multicast IP addresses (or addresses of multibroadcast services) to which it is already subscribed or the total bitrate that this terminal is already receiving. By proceeding in this way, the proposed system makes it possible to limit congestion in the case where it is possible to ascertain an estimate of the bitrate at the level of the access interface for each multicast IP address to which the terminal is already subscribed.
Such may be the case when the source IP address of the multicast transmission corresponds to a server implemented by a content provider or else by a network operator. Indeed, in this case it is possible to control the bitrate generated by the server.
However, this type of admission control does not make it possible to effectively avoid congestion on the access interface in the case where an arbitrary terminal of the network may itself become a source of multibroadcast service to which other terminals of the network may subscribe.
Indeed, under these conditions, it is not possible to estimate the bitrate generated by a source terminal of a multibroadcast service and that a subscriber might receive during the period of his subscription to this multibroadcast service.